The relative clay-mineral contents (rel%) of illite, smectite, chlorite and kaolinite were determined semi-quantitatively by calculating the integrated peak areas of the clay-mineral basal reflections, weighted with the empirically determined factors after Biscaye (1964, 1965). The quartz/feldspar ratio is the ratio of the quartz peak area over the sum of the peak areas of K-feldspar and plagioclase. K-feldspar/plagioclase also represents the ratio of the respective peak areas.